This invention relates generally to a method for resealing toner cartridges, such as the type used in laser printers, especially those in which the toner cartridge contains not only the toner or powder but also the ionizing means and photoreceptor drum in one package. The original seal design lends itself to lower cost maintenance of the printer or copying machine but significantly higher costs for replacing consumed toner.
While it is easy to remove the cartridge in a typical machine, and in fact this must be done in order to install a new cartridge, one would think most people would opt to refill their cartridges by adding toner themselves. Such is not the case, however, with most office personnel avoiding this task, if for no reason other than the difficulty of containing the inadvertent spilling of some of the toner, and the resultant soiling of hand, clothing and immediate surroundings. The spilling of toner is also the reason a seal must be provided if the cartridge is to be shipped or held in any position except in the normal or upright position. A simple, stiff, push-in, pull-out plastic seal is sometimes adequate, especially if hand or local delivery of the refilled cartridge is contemplated. However, this type of seal will not prevent toner spilling under even normal handling of a well packaged toner cartridge handled by postal or shipping organizations.
A second and very important marketing reason that a thick, single piece of plastic is not desired in refilled cartridges is simply the fact that users of these cartridges are familiar with the original manufacturer's pull-tab system and tend to be reluctant to switch to an off-brand component in their expensive and well-performing printer.
There is one method intended to nearly duplicate the original cartridge sealing system. It requires the splitting of the shell of the cartridge, often requiring extensive reworking of the mating surfaces, replacing and cementing a new styrene or similar gasket which provides the surface to which the new pull-tab seal is ultimately adhered to, and the assembly, via pressure sensitive adhesive of a "U" shaped, thin plastic seal. The split shells of the cartridge are then recemented and other, time-consuming adjustments on other components of the cartridge are performed to make it functional. Because of the high cost of splitting and reassembling these cartridges and the inevitable deterioration of the appearance of the finished toner cartridge, other ways have been sought for refilling these cartridges, to take full advantage of the potential price differential of new cartridges and those that have been refilled. Except in rare cases, the other expensive components that make up a complete toner cartridge are, in general, in excellent condition and capable of performing well for at least a few refillings of the cartridge. Also, the lifetime of a printer and use thereof is such that the costs of toner cartridges, in general, often exceed the cost of the printer.
To minimize costs and improve appearance, various attempts have been made to provide a U-shaped, insertable seal, that is close to the original manufacturer's design. There are ways others have developed and attempted to use, with varying degrees of success. Most have the common elements of using two thin plastic films, folded in a somewhat complex, but generally "U" shape, inserting the films into the unseparated cartridge with the aid of an insertion tool to push the two plastic films into the slot from whence the first plastic film, covering the pressure-sensitive-coated second film (the actual seal), is subsequently pulled. The use of two films, one covering the adhesive layer on the second film is necessitated by the fact that the adhesive coated film cannot be slid into the cartridge without damaging the film and adhesive layer.
A somewhat common problem associated with this sealing method is the complexity of folding the two-piece seal in just the right fashion and accuracy, without contaminating the pressure-sensitive adhesive generally used, and, upon pulling the cover film, to expose the adhesive-coated second film to the substrate to which it is to be adhered, without any wrinkles, other blemishes, or residual toner adversely affecting the sealing process. Another very common problem occurs when the pressure-sensitive adhesive prematurely makes contact and adheres at some point to the substrate so that the seal cannot be properly seated and must be removed, generally destroying the seal and making it unusable. In a worst case scenario, if more than a very small amount of pressure-sensitive adhesive makes improper contact with the substrate and the seal must be pulled out to replace it, it is very likely that the seal itself will rip when an attempt is made to remove the misaligned seal within the cartridge, making it extraordinarily difficult, if not impossible, to remove the torn section of seal within the cartridge without disassembling the cartridge. The tearing problem in this process can be minimized if one uses plastic film material like DuPont's Tyvek for the seal material, but then the seal no longer has the look and feel of the original manufacturer's seal, a characteristic of significant value in the marketplace.